They don't provide a dedicated tool specifically for the free version, however... for their consumer products, they provide only one dedicated uninstaller for the different versions.
For instance, "Bitdefender_2022_Uninstall_Tool.exe" is the dedicated uninstaller for "Bitdefender Antivirus Plus", "Bitdefender Internet Security" and "Bitdefender Total Security".
Although on their website they make a distinction between paid versions and trial versions, and between "Bitdefender Antivirus Plus", "Bitdefender Internet Security" and "Bitdefender Total Security" the uninstaller file is always the same (I've checked the SHA256).
The uninstaller changes from year to year though, you have "Bitdefender_2022_Uninstall_Tool.exe", "Bitdefender_2020_Uninstall_Tool.exe", "Bitdefender_2019_Uninstall_Tool.exe", and so on.
In short, I would say that the same uninstaller will work for the free version too (the uninstaller that's from the same year of the free version). Obviously, this is just an educated guess based on what I've explained above. I've opened a support ticket asking that question and will update here when I receive a reply.